Controllable pitch propeller



Jan' 5, 1942- G. T. LAMPTON ETAL 2,268,948 CONTROLLABLE PITGH PROPLLER Filed JuneA '7, 1957 4 Sheets-Sheef 2 Jan. 6, 1942. K G. T. LAMSTO-N T A Lv y 2,258,948

GONTROLLABLE FITCHV PROPELLER Filed June 7, 195'? @Sheets-Sheet 4 j mmm 52 N lf/7, 77:77

i? @im ofthe blades.

rotatable around the driving-element.

`on the propeller-blades.

Patented Jan. 6, 12942 `CONTRQLLABLE PITCH PROPELLER Glen T.- Lampton, Paul F. Hackethal, and :Arthur T. Briggs, Williamsport, Pa., assignors to Aviation Manufacturing Corporation, Williamsport, Fa., a corporation of Delaware .Application June 1, 1937, Serial No. 146,822

(o1. 17o-16s) 12 Cl'aims.

The invention relates to variable pitch propel- 1ers for airplanes.

One object 'of the invention is to provide in'l-l proved, eicient and simple -mechanism for effecting pitch-changes of the propeller blade by power derived from the propeller or propellershaft.

Another object of the invention is to provide improved pitch-change gearing which includes a very high-ratio speed reduction to minimize the power required for operating the pitch' change gearing.

Other objects of the invention will appear from the detailed description.

The invention consists in the several novel features which are hereinafter set forth and are more particularly defined by claims at the conclusion hereof.

In the drawings: Fig. l is a longitudinal section of a propeller embodying the invention.

Fig. 2 is a section on line 2 2 of Fig. 9 illustrating the pivoted friction-pulley set for driving the pitch-change gearing to increase the pitch Fig. 2"L is a similar view illustrating the friction-pulley set for decreasing the pitch of the blades. Fig. 3 is a perspective of a frictiondriving element which is xed'on and rotates with the propeller hub. Fig'. 4 is a perspective of the driven friction-element which is Fig. 5 is a sectional perspective of the gearing between the friction-driven element and the gear-segments section on linev 6-6 of Fig. 1. on line 1--1 of Fig. 1. Fig. 8 is a section online 8 8 of Fig. 1. Fig. 9 is a rear elevation of the variable friction-pulley and its mounting. Fig.

10 is a section on line IBL-I0 of Fig. 9. Fig. 1l is a section o line II-II of Fig. 9. Fig. 12 is a section on line |2-i2 of Fig. 1. Fig. 13 is a detail section of the pivotal mounting for the shifter yokesfor the friction-pulley. Fig. 14 is a detail perspective of the pivotal mounting for the yokes for shifting the friction-pulley.

The invention is exemplified in 'an airplane propeller comprising an engine-driven shaft a,

`a hub b keyed tothe shaft between wedge-collar b1. b2' and provided with radial sockets b3 and propeller blades c provided with Shanks cl which are supported in ball bearings c2, c3 in the sockets b3. vShaft a, which may be the engine shaft, is journaled in'a ball bearing a1 carried by a stationary housing a2 which may be a part of the engine casing. The outer races of Fig. 6 is a transverseI Fig. 7 is a section lli thrust-memberscA and the inner races of bearings c:3 are secured on studs b4 which are integral with'lthe hub b.

A bevel-gear segment c5 is adjustably fixed to the inner end of each blade shank c1. A

gear-ring d with external bevel-teeth d3 is rotatable in. the hub and relatively to the hub b and shaft a. Said teeth mesh with segments c5 on all of the propeller-blades to equidistantly and oppositely rotate the blades in the hub for pitch-variation. Gear-ring d is journaled on ball bearing 3| which is carried by the hub portion b5 within an extension b" of the hub. An internal series of gear teeth d1 are provided in a flange d2 at the inner vend of gear-ring d. A gear-ring e provided with internal gear-teeth e1 corresponding 'to those on gear-ring d is iixedly held in the hub b by'means of bolts e2 which pass through a flange e3 integral withv ring e and a head e4 at the inner end of the hub portion b".

The improved gearing for varying the pitch of the blades by power derived fromthe propeller-shaft `a comprises: a iriction driving element 20 which is provided with an integral hub or sleeve 2l which surrounds the hub portion b5 and is keyed to rotate with the hub b which rotates with'shaft a, and with a radial flange 22 having an annular convex drivingface 23on', one of its side faces; a complementary friction driven element 24 which is provided with a sleeve vor hub 25 journaled on and rotatable around hub 2| of driving element 20 and with an integral radial ange 26 having an annular convex vfriction-face 21 opposite and spaced from the friction-face 23 of'the driving element 20; and a friction-pulley or ring 28 which has conoidal friction-faces 29 and 30 on its opposite sides vwhich engage, respectively, the convex driving face 23 and the driven face 21 to drive element 24 from element 2n. This pulley or ring is pivotally mounted, as hereinafter described, so it canbe positioned to increase or vdecrease the speed of the driven elementl24 relatively Ato the driving element 20, the shaft a and hub b, which rotate together, by engaging the pulley with the driving face 23 and the driven face 21 at relatively different radii. Driving element 20 is conned against longitudinal movement on hub por,- tion b5 between a collar 3la on hub b and the inner race 32 which is securedon the hub. A- -ball bearing 34 is interposed between the outer 'end of hub 25 of driving element 24 and race 32 bearings cil are held in sockets b3 by'` outward 65 against opposite longitudinal movement.

ing of the ring h around said eccentric. Arotation of the eccentric 4I in the hub causes 1 the teeth h3 of the ring h to traverse the inon and concentric with the eccentric 4| by means of ball bearings h1. 'a series of external teeth h2 for meshing with Ring h isprovided with the internal teeth e1 ofthe ring e which is fixed in the hub b and with a corresponding series of teeth h3 meshing with the teeth d1 0f the gearring d which is rotatable in the hub to rotate the blades for pitch-changes. The external teeth lh2 and h3 on ring h are at least one less in number than the internal teeth on rings d and e and all of the teeth h2, h3, d1, el are of the type adapted for rolling contact as a result of the bodily rotation of the eccentric 4I and the roll- Each ternal teeth e1 on the ring e which is xed to the hub b and, by reason of the lesser number of teeth h3 on the eccentric-ring h, the latter will rotate in the hub and gear-ring e1 a distance corresponding to one tooth if that is the difference in the number of the teeth between h3 and e1. Teeth h2 and h3 intert with the teeth d1 of the ring d and teeth e1 of ring e at the point of maximum eccentricity of the ringv and clear at the points of minimum eccentricity.l Rotation of the eccentric 4| will cause the fixed ring e and its teethe2, which mesh with teeth h2, to rotate the eccentric ring h in the hub, a distance corresponding to the gear-tooth,'for each rotation of the eccentric 4| in or relatively to the hub, assuming the differential to be one more tooth in the rings e and. d than in the ring h. This rotation of gear-ring h in the hub will rotate gear-ring d with it. Ringd will rotate segments c5 to rotate the blades on their own axes for pitch-variation. When the element 24 and eccentric 4I rotate with the hub and not relatively thereto, the pitch-change gearing will remain inactive to keep the blades at their set pitch. The driven element 24 is provided with an integral counter-balance 25a to balance the mass of element 24 which carries the eccentric 4I.

The friction-faces 23, 21 are outwardly divergent and the friction-faces of pulley 28 are convergent to permit the pulley to be angularly adjusted while both of its faces remain in driving contact with faces 23, 21. Normally,'that is when no pitch-change is desired, the axis of pulley 28 is parallel to the axis of shaft a, the lines of contact on driving and driven-faces. 23, 2-1 are of equal radii or equidistant from the axis of shaft a. and the lines of contact on pulleyfaces 20, 30 are of equal radii or equidistant from the axis of the pulley, and the pulley will be neutral and rotate idly without producing any relativerotation' between the-driving and driven elements- 28, 24. Elements 20, 24 will rotate with the hub and shaft a and pulley 28 will rotate on its own axis, and hub b without effecting any relative movement. between said elements and, in consequence, the pitch-change gearing will remain ineffective or without pitch-changing movement. 'I'he gear-rings d, e, h will all rotate with the hub b and shaft a without operating the pitch-change gearing, so that vthe pitch ofthe blades will remain xed. l

When pulley 28 is`swung in one direction, as shown in Fig. 2, the radius of the contact line on driving face 23 is increased, the radius of the l contact line on pulley-face is decreased, the

radius of contact line on pulley-face 30 'is increased, and the radius of contact line on driven face 21 of element 2l is decreased. This will cause the pulley 28 to rotatethe driven element 24 and eccentric 4| in, and relatively to the hub, in the direction of rotation 'of the propeller so that the eccentric gear-ring h will be rotated within gear-ring e and advance the vgear-ring d in the hub and in the direction of rotation of the hub or rotate the ring d. faster than the hub. This will rotate segments c5 to increase the pitch of the blades. ,f y

When the pulley 28 is tilted in the opposite direction, as indicated in Fig. 2?-, the radius of the Contact line on driving face 23 will beiv decreased, the radius of the contact line on pulleyface 28 will be increased, the radius of the contact line on pulley-face will be decreased, and

the radius of the contact line on the face 21 of driven element 24 will be increased. In this position of pulley 28, element 24 and eccentric 4l will be rotate'd in and relatively to the hub b in the direction opposite `to the rotation of the propeller. This4 will cause the gear-ring d to be rotated by eccentric 4I at a lower speed than the hub b. The rolling movement of the gear-ring h in the gear-ring e which is fixed to the hub will then effect, through gear teeth h3 and gearteeth d1 on ring d,rotation of segments c5 to decrease the pitch of the blades.

Friction-pulley 28 is journaled'on a ball-bearing 42 which is carried by a hub 43. Said hub is supported by a universal or ball-and-socket joint 45 between said hub and a stud 46 which is fixed to the cross-member of 'a yoke 44. This universal joint permits pulley 28, when vthe yoke is shifted, to vary its angular relation with the convex friction faces 23, 21 of elements 28, 24. Yoke 44 is pivotally supported on coaxial pintles 48 to swing transversely of the pulley 28. When the yoke 44 is swung in either direction, the axis.

of thejoint 45 will be shifted longitudinally of shaft a and the angular relation between the friction faces on pulley 28 and the convex friction` faces 23, 21 will be varied to vary the radii of the contact lines between said faces for varying the speed of rotation of element 24 and eccentric 4l in the hub. The outer portion of the pulley remains. confined between elements 20, 24 while its axis is shifted by stud 48.v Tlie facesA 23,121 are outwardly divergent and the pulleyfaces are convergent. The universal joint 45 and the engaging portions of the friction faces of the pulley 28 and friction faces 23, 21 control the angular positionof the' pulley.l The yoke 44 is pivoted so it will swing the joint 45 longitudinally of shaft a to vary the radial lengths of the'lines of contact between the friction faces of the pulley and elements'20, 24 for speed *increase or decrease as hereinbefore described, and to keep both faces of pulley 28 in operative contact with faces 23, 21, respectively.

Fluid pressure mechanism may be used to shift yoke 44 to control the angular settings of pulley 28 for variably operating the pitch-change gearing. This mechanism comprises a cylinder 8| integrally. formed with a head 52 with a piston 62, a stem 83 pivoted at 441 to yoke 44 and held by a spring 64in thrust-engagement with said ste'm. Spring 64 is interposed between a flange on the inner end of stem 83 and a cap 64a which is fixed to head 52.

Fluid under pressure, vusually oil, is supplied I a duct 58 and'extends' around the' chamberin sure of the fluid in the cylinder. will hold yoke 44 in position to retain the pulley 28 in its neutral position against the force of spring 64; upon an increase of pressure will shift the yoke to the position shown inFig. 2 for increasing the pitch of the blades, or upon reduction of the pressure, the spring 64 will shift yoke 44 and pulley 28 into the position shown ein Fig. -2a to decrease the pitch of the blades.

The drive-pulley 28 and the portion of elements 20, 24 engaged thereby and the means for shifting pulley 28 are disposed around the portion b4 of4 hub b and between the hub-portion blwhich surrounds gear-rings d, e and the casing or wall L2 and are enclosed by an intermediate housing 53 which is secured to casing a2 and carries a sealing ring 60 which engages an axial ange on the head e4 which is angular in crosssection and fixed to the inner end of portion b" of hub b.

Studs 50 are fixedly secured in supporting arms 5|. The controlling element for shifting yoke 44 comprises a yoke 54 which is xedly clamped to the eccentrics or short arms 49. When yoke 54 is swung on studs 50 as an axis, the pintles 48, to which the ball bearing yoke 44 is pivoted, the inner pivoted end of the yoke will swing to and from the axis of the driving and driven elements 20, 24 while permitting the yoke 44 to rock on pintles 48 and in the socket of the universal joint 45 and the conoidal faces of pulley 28v to adjust themselves for .the varying contactwith the faces 23, 21 on different radii'. =The Iangle of the yoke .44, universal joint 45, hub 43 and pulley 28 when the yoke 45 is rocked, controls the speed and also shifts its axis slightly to and from the driving and driven elements to provide for proper contact on different radii between the pulley faces and the driving and driven elements as hereinafter described. In order to provide for effective frictional contactA or loaded engagement between the pulley 28 and the friction surfaces 23, 21 yin all positions ofthe pulley, devices are. provided for pressing the pintles 48, on which the yoke 44 is pivoted,l toward the axis ofV ther propeller shaft a.- This means comprises a yoke 54 which straddles yoke 44 and is clamped to a pair of coaxial pivotmembers 49 which carry 4 the pivot-pins 48 f or the shifter-yoke 44 and are pivotally mounted on studs 54a which are offsetv from or eccentric Ato pivot-pins 48 for yoke 44. Studs 54El are fixedly held in supporting arms 5| onv head 52.- A

second cylinderV 1|| with a piston 1| is provided`6 in head 52. A spring 13 is interposed between" piston 1| vand yokeI 54. Oil under pressure corresponding to the pressure in cylinder 6| flows to the closed end of cylinder 1|) `from duct 69 which supplies oil to cylinder 3|. Astop-ring 12 limits vthe outward movement of, piston 1|. The spring 13 and the uid pressure in cylinder apply yielding pressure to the4 yoke 54 which is clamped to the pivot-members 49 to rock said members around xed pivots 54a and move pivotpins 48 toward the axis of propeller-shaft a, so that the friction-faces 28, '29 of pulley 28will `be spring-loaded or yieldingly forced into engagement with friction-surfaces 23, 21 to insure pulley and said surfaces. in all angular settings of the pulley. Spring T3 is suflicient, under var-A iations of pressure in cylinder 6|, to exert suricient yielding pressure on yoke 54 to force pulley 5 28. against surfaces 23, 21. Oil is circulated through the chamber in the hub between hubportions b5 `and b" which contain the pitchchange gearing and the chamber in housing 53 which surrounds the elements 20, 24 and the l0 pulley 28, by `any suitable means, as well understoodI in the art, to lubricate said gearing.

` Pulley 28 and its mounting, including yoke 44,

v its operating mechanism,'including cylinder 8|,

l ypiston 62, stem 63, and spring 54, are mounted won head 52 which is secured to 'theintermediate housing 53 to permit the vunitary removal of l' all,v of the parts carried by'said head for inspec` tion or repair. The head closes the opening in *the housing 53 through which said parts are insertable or removable.

" Apin 80 is screw-threaded into. head 52 and is provided with stops 8| for limiting the movement of 'the yoke 44. The outer end of said pin is splined to alcap 82 which isrotatably mounted in the front-wall of housing 53. By rotating the cap, the pin can be adjusted to varythe limit of angular movement of pulley 28 relatively to theelements 20, 24. e

In operation, the pressure of the fluid supplied 3U to cylinder 6|, whenthe propeller-blades are set at the desired pitch, will be such that piston 62 and yoke 44Will be set to retain the pulley 28 in its neutral position between the driving and driven elements 28, 24.` This will cause the radii :grof the contacting lines of the pulley and fric-l tion-faces 23, 21, respectively, to be the same so that' the elements will rotate together with the hub and at the same speed andthe pitch-changing gearing will remain fixed. When an increase 4u of pitch is desired, the pressure o f the fluid in cylinder 6|' will be increased to shift pu1ley28 into position shown in Fig. 2. Driyen element 24 and eccentric 4| will then be rotated in, and .'relatively to, the hub, to operate tlie bevelled is-gear-ring d to increase the pitch of the blades.

When the pitch has been increased to the desired limit, pulley 28 will be restored to its neutral position by the reduction of pressure of the fluid in cylinder 6|. When a pitch-decrease is n desired, the pressure of fluid in Vcylinder 6| Will be further reduced and pulley 28 will be shifted in the position shown in Fig. 2a. l ment 24 and eccentric 4| will then be rotated inthe propeller-hub in the direction'of vrotation 5 3 of the propeller but at` a lowerspe'ed,v to rotate ring d so it Will decrease the pitch of the blades. Whenthe pulley 28 is set to increase the pitch of the blades, it will `rotate the eccentric in the hub in the direction of rotation of the propeller and,

0 as a result, the speed of the eccentric will be greater than the hub.

The invention exemplifies: improved pitchchange mechanism which comprises an eccentric rotatable relatively`` to the propeller-hub and 65 gear-rings fixed and rotatable in the hub, re-

spectively. for increasing er decreasing the pitch of the blades; simple, friction-driven gearing with an angularly adjustable dsuble-facefrictien-pulley for increasing or decreasing4 the speed cf rotation of they eccentric in,.or relatively to, the propeller hub; simple gearing, by which a very high ratio speed-reduction from thepropeller-hub or shaft is utilized for operating the speed-change gearing; a gearing which themaintenance of driving contact between the 76 includes an eccentric gear-ring which remains Driven ele- The invention is not tobe understood as re-x stricted to the details set forth, since these may be modif-led within the scope of the appended claims; without departing from the spirit and scope of the invention.

Having thus described the invention, what we claim as new and desire to secure by Letters Patent is:

p 1-. In a controllable pitch propeller, the combination with a shaft, a hub rotatable' by the shaft and propeller blades rotatably mounted in the hub for pitch variation, of a driving element around and fixed tov the shaft, a driven element around and rotatable relatively to the shaft, said elements having confronting friction faces on their sides, gearing operable by said driven element for rotating the blade for pitch-variation, an idler pulley having friction faces -on opposite sides thereof between, and for respectively engaging, the confronting friction faces of said element and angularly movable to engage relatively different radii of its faces with the confronting faces of the elements on relatively different radii of the elements for driving the driven element at different speeds to operate the gearing for pitch-variation, and means for shifting the pulley angularly to drivethe driven element at different lspeeds for pitch-variation and for pressing the pulley angularly to force its opposite faces into engagement with the confronting faces of the elements, respectively.

2. In a controllable pitch propeller, the combination with a shaft, a hub rotatable ly the shaft and propeller blades rotatably mounted in the hub for pitch-variation, of a driving element around and fixed to the shaft, a driven element around and rotatable relatively to the shaft,

' said elements having confronting conver' out- .wardly divergent friction faces on ytheir sides,

gearing operable by said driven element forl rotating the blades for pitch-variation, an -idler pulley having outwardly convergent friction faces on opposite sides thereof between, and for re-l spectively engaging, the confronting friction faces of said element and angularly movable to engage relatively different radii of its faces with the confronting faces of the elements on relatively different radii of theelements for driving the driven element at different speeds to operate the gearing for pitch-variation, and means for' shifting the pulley angularly to drive the driven element at different speeds for pitch-variation, and for pressing the pulley angularly to force its opposite faces into engagement with the ccnfronting faces of the elements, respectively.

3. The combination with a shaft, a hub rotatable with thel shaft and propeller blades rotatably mounted in the hub for pitch variation, of pitch-changing mechanism comprising a pair of coaxial relatively rotatable friction elements having confronting divergent friction faces, and a pulley provided on its opposite sides with friction faces, outwardly convergent relatively to each other, each face being adapted to engage only one of the elements, the pulley being supported to rotate on an axis substantially parallel with the axis of the friction elements to respectively engage its opposite faces with the faces on thev friction elements on an 'equal radius and for angular movement to engage its opposite faceswith the elements, respectively, on relatively different radii for driving one of the elements from the other at different relative speeds, and means for shifting the pulley to control the pitchchanges. f

4. The combination with a shaft, a hub rotatable with the shaft-and propeller blades rotatably mounted in the hub for pitch-variation, of pitchchanging mechanism comprisingl a pair of coaxial relatively rotatable friction elements having confronting divergent convex friction faces, and a pulley provided on its opposite sides with friction faces, outwardly convergent relatively to each other, each face being adapted to engage only one ofthe elements, the pulley being supported to rotate onan axis substantially parallel with the axis of the friction elements to respectively engage its opposite faces with the faces on the friction elements on an equal radius and for angular movements to engage its. opposite faces with thel elements, respectively, on relatively different radii for driving one of the elements from the other at different relative speeds, and

Vmeans for shifting the pulley to control the pitchengage only one of the elements, a bearing at the longitudinal center of the pulleyon which the pulley is supported for universal pivotal movement, to rotate on an axis substantially parallel with the axis of the friction elements to respectively engage its'opposite faces with the faces on the friction elements on an equal radius, and for angular movement to engage its opposite faces with the elements, respectively, on

relatively different radii for -driving one of the elements from-the other at different relative speeds, and means for shifting the bearing to shift the pulley and control the pitch-changes.

6. The combination with a shaft, a hub rotatable with the shaft and propeller blades rotatably mounted in the hub for pitch-variation, of pitch-changing mechanism comprising a pair of coaxial relatively rotatable friction elements having confronting divergent friction faces, and a pulley provided on its opposite sides with friction faces, outwardly convergent relatively to each other, each face being adapted to engage only one of the elements, an arm on which the pulley is pivotally supported, a pivoted support forthe arm' on which the arm is eccentrically pivoted, the pulley being rotatable on an axis substantially parallel with the axis of the friction elements lto respectively engage its opposite faces with the faces on the friction elements on,

the pivoted support to shift the pulleyand control the pitch-changes.

'7. The combination with a shaft, a hub rotatable with the shaft and propeller blades rotatably mounted in the hub for pitch variation, of pitch-changingmechanism comprising a pair of coaxial relatively rotatable friction elements having confronting divergent friction faces, and

a pulley provided on its opposite sides with friction faces, outwardly convergent relatively to each other, each face being adapted to engage only one of the elements, the pulley being supported to rotate on an axis substantially parallel with the axis of the friction elements toV respectively engage its opposite faces with the faces on the friction elements on an equal radius and for angular movement to engage its .opposite faces with therelements, respectively, on relatively different radii for driving one of the ele' ments from the other at different relative speeds, means for shifting the pulley to control the pitch-changes, and means for yieldingly pressing the pulley toward theaxis of the elements.

8. The combination with a shaft, a hub rotatable with the -shaft and propeller blades rotat-y c ably mounted in the hub for pitch-variation, of

pitch-changing mechanism comprising `a pair of coaxial relatively rotatable friction elements having confronting divergent friction faces, an eccentric rotatable with one of said elements, gearing operable by the eccentric for rotating the blades in the hub, and a pulley provided on its opposite sides with friction faces, outwardly convergent relatively to each other, each face being adapted to engage only oneof the elements, the pulley being supported to rotate on an axis substantially parallel with the axis of the friction elements to respectively engage its opposite faces with the faces on the friction elements on an equal radius and for angular movement to engage its opposite faces with the elements, respectively, on relatively different radii for driving one of the elements from the other at different relative speeds, and means for shifting the pulley to control the pitch-changes.

9. 'Ihe combination with a shaft, va hub rotatable with the shaft and propeller blades rotatably mounted in the hub for pitch-variation, of pitch-changing mechanism comprising a pair of coaxial relatively rotatable friction elements having confronting divergent friction faces, and a pulley provided on its opposite sides with fric-- tion faces, outwardly convergent relatively to' each other, each facevbeing adapted to engage only one of the elements, the pulley being supported to rotate on an axis substantially parallel with the axis of the friction elements to respectively engageits opposite faces with the faces on the friction elementson an equal radiusand for angular movement to engage its opposite faces with the elements, respectively', on relatively different radiifor driving one of the 'elements from the other at different relative speeds,

means for shifting the pulley to control thepitch-changes, and a stationary housing for said elements and pulley comprising a removable secable with the shaft and propeller blades rotatably mounted in the hub for pitch variation, of pitch-changing mechanism comprising a pair of coaxial relatively rotatable friction elements having confronting convex divergent friction faces, and a pulley provided on its opposite sides with outwardly facing conical friction faces, each face being adapted to engage only one of the elements, the pulley being supported to rotate on an axis substantially parallelwith the axis of the friction elements to respectively engage its opposite faces with the faces on the friction elements on an equal radius and for angular movement to engage its opposite faces with the elements, respectively, on relatively different radii for drivingy one of the elements from the other at different relative speeds, and means for shifting the-pulley to control the pitch-changes.

11. The combination with a shaft, a hub rotatable with the shaft and propeller blades rotatably mounted in the hub for pitch-variation, of mechanism for effecting pitch-changes of the blades comprising a pair of relatively rotatable friction elements around and coaxial with the shaft and having confronting divergentl friction faces,one of said elements being driven bythe shaft anda pulley between said elements having, on its opposite sides, outwardly facing conical side faces each engaging only one of the elements, said pulley being normally supported to rotate on an axis parallel to the axis of the shaft and angularly movable with respect to the axis of said elements to vary the radii of the contacting line between the pulley 'and the elements,

'by the shaft and a pulley between said elements having outwardly facing conical side faces each engaging only one of the elements, said pulley being normally supported to rotate on an axis parallel to the axis of theshaft and angularly movable lwith respect to the axis of said elementsy to vary the radii of the contacting line between the.'` pulley and the 'elements for driving one of the elements from the other at different relative speeds, and means for shifting the pulley angularly relatively to its normal axis to control the pitch-changes.

GLEN T, LAMPTON. l

PAUL F. HACKETHAL.

ARTHUR T. BRIGGS. 

